The field of the present invention is valve systems for internal combustion engines and, more specifically rotary valve systems.
Poppet valves have been almost universally employed on four-stroke internal combustion engines, principally because of good sealing properties. However, with modern high-speed engines, poppet valves exhibit certain disadvantages as well. Exhaust poppet valves constantly facing the combustion chamber can become overheated and promote preignition. The requirement that such valves have both valve shafts and valve heads always located in the opening and passage of the porting affects intake and exhaust efficiencies. Furthermore, disadvantageous flow characteristics result from the circuitous flow path required by such valve configurations. Such valves also develop substantial impact noise upon closing.
To solve the foregoing difficulties with poppet valves, recurring efforts have been undertaken toward construction rotary or sleeve valves. Such efforts have been directed to ball valves, cylinder valves, conical valves, disc valves and the like. However, such valves which are sufficiently compact for internal combustion engines tend to have inefficiencies in the relative portion of time during which such valves are opening and closing as distinguished from remaining open.
One such prior valve is illustrated in FIGS. 5 and 6. A ball-type valve body 1 includes a through bore 2 with an outer spherical sliding surface 3 around the bore. The rotary valve A thus constituted is rotatably held in the seat members 7 and 8 and the spherical sliding surface 3 contacts the upper and lower seat members 7 and 8 in the receiving area of the intake or exhaust passage 5.
In the device illustrated in FIGS. 5 and 6, the rotary valve A is rotated intermittently by a driving means. When the valve rotates, air/fuel mixture in the case of an intake passage may flow into the combustion chamber 4 via the through bore 2. However, the air/fuel mixture must flow entirely through the through bore 2 which, as oriented in FIG. 6, exhibits a relatively small effective cross-sectional flow area. Consequently, the opening and closing times are such that the rate of flow limits efficiency. The circular nature of the conventional through bore 2 in combination with the circular seat associated therewith presents a small cross-sectional opening as the valve is opening or closing. The cross-sectional area of the opening associated with such a conventional valve is illustrated in FIG. 12.
Oldham coupling devices have been employed in rotary valve applications in internal combustion engines to provide a rotational interlock between the driving mechanism and the valve body. Such devices allow for axial misalignment between components and, to that end, require some clearance for movement of the components transverse to the rotational axis of the valve. With such clearances and through the use of meshing gears for driving such a system, backlash with the inherent impacts on the components associated therewith can also become a problem in rotary valve mechanisms.